The normal range of amniotic fluid depth in the 6th month of pregnancy is between 2cm and 8cm. Amniotic fluid depth less than 2cm is considered too little amniotic fluid; if more than 8cm is too much amniotic fluid, both too little and too much amniotic fluid are abnormal conditions. Due to the increased uterine tension, complications of hypertensive disorders in pregnancy are three times higher than in normal pregnancies, and can also complicate premature rupture of the placenta and increase the likelihood of preterm delivery. In case of sudden rupture of membranes, the pressure in the uterine cavity can suddenly decrease, which can lead to placental abruption and shock. Excessive amniotic fluid can be complicated by fetal malformation, abnormal fetal position, umbilical cord prolapse, fetal distress, and many other adverse consequences. Low amniotic fluid occurs in the middle and late stages of pregnancy and can cause pressure around the uterus to act directly on the fetus, causing skeletal and muscular malformations, such as oblique neck, curved back, hand and foot deformities. In severe amniotic fluid hypohydramnios, there is a high incidence of fetal malformations, such as typical Potter syndrome caused by congenital renal agenesis, fetal lung hypoplasia, flat nose, low position of large ears, underdeveloped kidneys and ureters, as well as shovel-shaped hands and bowed legs. Low amniotic fluid can also lead to fetal lung hypoplasia and fetal growth restriction. When the amniotic fluid volume is less than 50 ml, the incidence of fetal distress can be as high as 50% or more.